This invention relates to an aircraft instrument, and more particularly to a novel attitude reference instrument which determines the aircraft's instantaneous pitch and roll angles from a plurality of measured aircraft velocities. Some of the velocities are obtained from a satellite navigation system, for example, the Global Positioning System, known as the GPS NAVSTAR, and other of the velocities are obtained from on-board velocity measuring equipment, for example a Doppler radar sensor, which may form a portion of a standard Doppler navigator, for example, the AN/ASN-128.
The invention provides an attitude reference which is not directly dependent on the use of gyroscopes and thus obviates many of the disadvantages of these instruments. For example, gyroscopes are subject to tumbling if the aircraft exceeds certain limits of pitch and/or roll, as well as precession and drift errors.
The present invention can function as a redundant backup system for a conventional gyro type attitude reference and can also be used for dynamic calibration and alignment of such a gyro attitude reference.
A co-pending application of the present inventor entitled, HYBRID VELOCITY DERIVED HEADING REFERENCE SYSTEM, Ser. No. 246,518, filed Mar. 23, 1981, discloses and claims a system for deriving a heading reference from velocities obtained from a satellite navigation system such as the GPS NAVSTAR, as well as other velocities obtained from on-board velocity measuring means such as a Doppler sensor.